JPH10239589A - Interference microscope - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily confirm the observation portion of a sample. SOLUTION: This interference microscope is provided with a laser oscillator 1 generating coherent light with a fixed frequency, a light source 3 generating incoherent light, a half-mirror 2 dividing the light generated from the laser oscillator 1 into object light and reference light, the first lens 8 radiating the object light and the light generated from the light source 3 to a sample 7, the second lens 10 radiating the reference light to a plane mirror 9, a light detector 11 detecting the interference light between the object light reflected on the sample 7 and the reference light reflected on the plane mirror 9 and the light from the light source 3 reflected on the sample 7, a computer 13 calculating the phase from the output of the light detector 11, and an X-Y stage 15 moving the sample 7 in the directions X, Y against the incident light while the direction vertical to the light radiating the sample 7 is set as the X-Y plane.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an interference microscope apparatus for imaging irregularities on the surface of a sample using light.

[0002]

2. Description of the Related Art Conventionally, as an apparatus for interfering an object light beam and a reference light beam and observing unevenness of a sample using the phase of the light beam, VRTychinsky, INMasalov, VLPankov and
DVUblinsky: OPTICS Comm., Vol. 74, (1989), pp. 37-40.
Is known. As shown in FIG. 3, the apparatus includes a laser oscillator 21 for generating a coherent plane wave of a constant wavelength, and a half mirror 22 for decomposing a laser beam generated from the laser oscillator 21 into two, an object beam and a reference beam. Is provided.
A first lens 23 is disposed on the optical path of the object light beam reflected by the half mirror 22, and the object light beam is
3 and enters the sample 24. The object light beam incident on the sample 24 is reflected on the surface of the sample 24, and
A light detector 25, such as a CCD, on which the reflected light passing through 3 is incident, is provided. On the other hand, a second lens 26 is arranged on the optical path of the reference light beam transmitted through the half mirror 22, and the reference light beam enters the reference plane mirror 27 through the second lens 26. Then, the reference light beam reflected by the reference plane mirror 27 passes through the second lens 26 again, is reflected by the half mirror 22, and enters the photodetector 25. The photodetector 25 detects a signal in which the object light beam reflected from the sample 24 and the reference light beam reflected from the reference plane mirror 27 interfere with each other. A memory 28 is connected to the photodetector 25,
The result detected by the light detector 25 is stored. Further, a computer 29 is connected to the memory 28, and the computer 29 obtains a phase from the interference intensity of the memory 28.

At this time, assuming that the wavelength of the laser beam generated by the laser oscillator 21 is λ and the phase resolution is m, the resolution D of the irregularities on the surface of the sample 24 can be obtained by the following equation (1). D = mλ / (4π) (1)

Here, if the wavelength: λ is 630 nm and the phase resolution: m is 5 ° (0.087 rad), the resolution D of the unevenness is about 4 nm, and the resolution of the unevenness is very high. The direction perpendicular to the surface of the sample 24 is the Z axis,
When the X and Y axes are taken in parallel to the surface of the lens, the resolution in the Z axis direction is very high in this method, but in the X and Y directions, the wavelength of the laser beam: Resolution. VRTychinsky: OPTICS Comm., Vol. 74, (1989), pp. 41 to increase the resolution in the X and Y directions
Or VRTy using phase as described in -45
As described in chinsky: OPTICS Comm., Vol. 81, (1991), pp. 131-137, a method using polarized light has been devised.

[0005]

However, the conventional phase interference microscope has the following problems. When the laser beam is split into two beams, a reference beam and an object beam, and at least one of the beams is converged and irradiated on the sample, the converged laser beam becomes a jinc function as shown in FIG. At this time, the portion irradiated on the surface of the sample by the laser light has a size about the wavelength of the laser light, and the magnification of the interference image needs to be several thousand times in order to observe the interference image. For this reason, there is a problem that it is very difficult to understand which part of the sample is being observed.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems of the prior art, and has as its object to provide an interference microscope apparatus capable of easily confirming an observation site of a sample.

[0007]

In order to achieve the above object, an interference microscope according to the first aspect of the present invention comprises: a first light source for generating coherent light at a constant wavelength; A second light source that generates coherent light, a unit that divides the light generated from the first light source into an object light beam and a reference light beam, and converts the light generated from the object light beam and the light generated from the second light source into a sample. Means for irradiating the reference beam to a reference object or a sample, and interference light between the object beam reflected by the sample and the reference beam reflected by the reference object or sample and the second beam reflected by the sample. A light detecting means for detecting light from the light source; a phase calculating means for calculating a phase from an output of the detecting means; a direction perpendicular to the light irradiating the sample being an XY plane; Moving means for moving to Y It was constructed with.

According to a second aspect of the present invention, there is provided an interference microscope according to the first aspect, wherein the second light source turns on light generation.
An opening / closing means for turning off is provided.

In the configuration of claim 1 according to the present invention,
A light beam of coherent light (laser light) having a constant wavelength generated from the first light source is divided into an object light beam and a reference light beam, and one of them is converged to one point and irradiated onto the sample, and at the same time, the light is input from the second light source. The sample is illuminated with coherent parallel light as normal epi-illumination. The reflected reference light beam and the object light beam interfere with each other and are incident on the detection means, and at the same time, the image by the incident illumination is detected by the same detection means. Thus, the image detected by the detecting means is an epi-illumination image,
The interference image of the laser spot becomes an overlapping image. Then, by confirming the position of the sample in the incident illumination image, it is possible to confirm which position of the sample is to be measured.

In the configuration of claim 2 according to the present invention,
As in the operation of claim 1, after confirming the measurement position of the sample, when starting the measurement, the second light source is turned off by the opening / closing means,
Use laser light only.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described with reference to FIG. FIG. 1 is a block diagram showing a phase interference optical system provided in the interference microscope device of the present embodiment.

In the interference microscope apparatus according to the present embodiment, a laser oscillator 1 as a first light source for generating a coherent plane wave of a constant wavelength, and a laser beam generated from the laser oscillator 1 are used as an object beam and a reference beam. A half mirror 2 is provided as means for splitting into two light beams.
In addition to the laser oscillator 1, a light source 3 including a light bulb such as a halogen lamp as a second light source that generates incoherent light close to white light is provided.
The switch 4 for turning ON / OFF the switch is connected. In front of the light source 3, a condenser lens 5 for converting light generated from the light source 3 into parallel light, and a second mirror 6 for irradiating the sample 7 with parallel light emitted from the condenser lens 5 are provided. Between the half mirror 2 and the sample 7, there is provided a first lens 8 for irradiating the object surface, which is one of the light beams split by the half mirror 2, and the light from the light source 3 to the sample surface of the sample 7. ing. Further, a second lens 10 is provided for irradiating a reference light beam which is another light beam split by the half mirror 2 to a plane mirror 9 serving as a reference object.

Further, interference between the reflected light of the object light beam reflected by the sample surface of the sample 7 and the reflected light of the reference light beam reflected by the plane mirror 9 is detected, and the light source 3 reflected by the sample 7 is detected.
A light detector 11 such as a CCD is provided as light detection means for detecting reflection of light from the light source. An A / D converter 12 for converting the output of the photodetector 11 into a digital signal is connected to the photodetector 11, and the A / D converter 12 is a computer as a phase calculation means for storing images and performing calculations. 13 is connected. The computer 13 is connected to a display unit 14 for displaying the captured image and the calculation result.

If the direction in which the illumination light (the reference light beam and the light from the light source 3) is incident on the sample 7 is the Z-axis, and the XY plane is parallel to the surface of the sample 7, the sample 7
Is provided with a two-dimensional XY stage 15 as moving means for moving the
A Z moving unit 16 for adjusting the focus of the sample 7 is connected to the two-dimensional XY stage 15.

Next, the operation of the present embodiment having the above configuration will be described. The laser light generated by the laser oscillator 1 is split into two by a half mirror 2 and the half mirror 2
And the reference light beam transmitted through the half mirror 2. The object light beam passes through the first lens 8 and enters the sample surface of the sample 7, and the reference light beam passes through the second lens 10 and enters the plane mirror 9. The object light beam incident on the sample surface of the sample 7 is reflected on the sample surface, passes through the first lens 8 again, passes through the half mirror 2, and is incident on the photodetector 11. The reference light beam incident on the plane mirror 9 is reflected by the plane mirror 9, passes through the second lens 10 again, is reflected by the half mirror 2, and enters the photodetector 11. On the other hand, light generated from the light source 3 such as halogen becomes parallel light by the condenser lens 5, is reflected by the second mirror 6, passes through the first lens 8 like the object light, and becomes incident illumination light of the sample 7. Then, the reflected light of the epi-illumination light reflected by the sample 7 passes through the first lens 8 and enters the light detector 11.

On the display unit 14, an image of the incident illumination reflected from the sample 7 is observed, and the laser beam (object beam) reflected by the sample 7 and the reflected beam (reference beam) from the plane mirror 9 interfere with each other. An interference image is observed. Here, since the reflected light having a constant phase is returned from the plane mirror 9, a change in the intensity of the interference light forming the interference image indicates irregularities on the sample surface of the sample 7. The photodetector 11 converts the change in the interference intensity and the image of the epi-illumination into an electric signal, and the A / D converter 12 converts the image into a digital signal, which is stored in the computer 13. The computer 13 displays the captured image on the display unit 14.

Before measuring the surface of the sample 7 with interference light,
Focusing on the surface of the sample 7 is performed by moving the XY stage 15 in the Z direction by the Z moving unit while observing the image on the display unit 14. In this state, as shown in FIG. 2, the display unit 14 displays an image obtained by epi-illumination and an interference image formed by a laser spot 17 of a laser beam. Then, the laser spot 17 is irradiated on the portion of the image displayed on the display unit 14 to be measured so that the laser spot 17 is irradiated.
Move the stage 15. When the laser spot 17 moves to a target position to be measured, the light source 3 of the epi-illumination is turned off by the switch 4 and only the laser illumination by the laser oscillator 1 is performed. At this time, only the interference image of the laser light is input to the light detection unit 11. In this state, the interference image is taken into the computer 13, the phase is obtained from the interference image, converted into height information by the above equation (1), and the result is displayed on the display unit 1.
4 is displayed.

According to the embodiment of the present invention, before starting the measurement of the sample 7, by observing the image of the normal epi-illumination and the laser spot 17 at the same time, it is possible to determine which part of the sample 7 is to be measured. It can be easily set. Further, since the light source 3 for epi-illumination can be turned on and off, the measurement is not hindered by interference light of laser light.

In the present embodiment, the laser beam from the laser oscillator 1 is split into an object beam and a reference beam by the half mirror 2 to irradiate the object beam onto the sample 7 and the reference beam is reflected by the plane mirror 9. Was configured to irradiate
The present invention is not limited to the above configuration, and a polarizing plate is arranged between the laser oscillator 1 and the sample 7 to divide the laser beam from the laser oscillator 1 into an object beam and a reference beam to detect the phase. Nomarski method can also be implemented. It is also conceivable to change the magnification by making the first lens 8 interchangeable so that the positioning is initially performed at a low magnification and gradually increased to a high magnification. This makes the alignment easier. Of course, various modifications and applications can be made without departing from the spirit of the present invention.

[0020]

As described above, according to the interference microscope apparatus of the present invention, it is possible to simultaneously observe the image formed by the epi-illumination by the parallel light and the interference image of the laser beam spot. It is possible to easily confirm which part of the sample is to be measured.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a phase interference optical system provided in an interference microscope apparatus according to an embodiment of the present invention.

FIG. 2 is a diagram illustrating an interference image between an image by incident illumination and a laser spot displayed on a display unit according to the embodiment of the present invention.

FIG. 3 is a block diagram showing a conventional phase interference optical system.

FIG. 4 is a diagram showing the intensity of converged laser light.

[Explanation of symbols]

 Reference Signs List 1 laser oscillator 2 half mirror 3 light source 4 switch 5 condenser lens 6 second mirror 7 sample 8 first lens 9 plane mirror 10 second lens 11 photodetector 12 A / D converter 13 computer 14 display 15 X ―Y stage 16 Z moving part

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[Procedure amendment]

[Submission date] April 4, 1997

[Procedure amendment 1]

[Document name to be amended] Drawing

[Correction target item name] Fig. 1

[Correction method] Change

[Correction contents]

FIG.

Claims (2)

[Claims] 1. A first light source for generating coherent light at a constant wavelength, a second light source for generating incoherent light close to white light, and an object light for generating light from the first light source. Means for dividing the object beam and light generated from the second light source into a sample, means for irradiating the sample with the reference beam, and reflection on the sample. Detecting means for detecting interference light between the detected object light beam and the reference light beam reflected by the reference object or the sample and light from the second light source reflected by the sample, and phase calculating means for calculating the phase from the output of the detecting means And a moving means for moving the sample in the X and Y directions with respect to the incident light with the direction perpendicular to the light irradiating the sample as the XY plane. 2. An interference microscope apparatus according to claim 1, wherein said second light source includes an opening / closing means for turning on / off the generation of light.